Just received a D4M, and for anyone considering the D4 or the D4M, you won't be disappointed. I've been using a BH-40 for years. As with other ball-head configurations, it is difficult to fine tune. I'm a stickler for precise composition using Live View for focus. Something as simple as leveling the camera takes multiple efforts and precious battery juice! When the D4M came out, it got my attention. I finally bit the bullet (it is a tad heavy for my backpacking demands and it is not inexpensive!). It is the finest piece of machined hardware I have ever operated. Camera adjustments are now precise and rapid, not to mention the absence of frustrating "camera flop". Arca-Swiss hit a homerun with the D4/D4M.